The use of laser devices for rangefinding purposes is well known in the prior art. To be effective, these devices should have certain desirable qualities. Specifically, these devices should be small, lightweight, easy to manufacture. Additionally, the devices should produce a pulsed laser beam that has good output power and a high pulse repetition rate for increased range capability. Superimposed over these requirements are eye safety considerations, which require that the device generate and transmit a laser with a wavelength of over 1.4 microns (λ>1.4 μm).
Previous laser transmitters used in rangefinding have had some, but not all, of these characteristics. For example, some flashlamp-pumped solid-state laser devices have been used to generate a laser beam for rangefinding purposes. However, although solid-state lasers effectively generate a single laser pulse, they are not capable of a multiple-pulsed laser beam without adding cumbersome cooling systems, which increases the size and power requirements of the laser transmitter.
Diode-pumped solid-state lasers lead to more efficient operation and therefore can be smaller and lightweight. Neodymium:Yttrium-Aluminum garnet (Nd:YAG) lasers are now commercially available for producing a pulsed laser beam for rangefinding purposes. The devices, however, produce a laser beam with a wavelength of approximately 1.0 micron (λ˜1.0 μm), which is not considered eyesafe at the increased output power required for certain rangefinding applications (over one kilometer). Additionally, diode-pumped solid-state lasers often do not operate over a wide range of environmental temperatures without incorporating inefficient and cumbersome temperature controls into the device.
The paper “1.55 μm Passive Q-switched Microchip Laser”, written by Ph. Thony, et al. and presented in Optical Society of America, Vol. 19, pp. 150-154, discloses diode pumped Erbium:Ytterbium micro-chip lasers which are small and yet are capable of producing a pulsed laser beam at an eyesafe wavelength (λ˜1.55 μm) by using passive Q-switching. However, these devices cannot produce a pulsed laser beam with sufficient pulsed power for rangefinding at over one kilometer.
In light of the above, it is an object of the present invention to provide a diode-pumped microlaser that can be used for rangefinding purposes. It is another object of the present invention to provide a diode-pumped microlaser which provides an output pulsed laser beam with a wavelength which is eyesafe to the operator. Yet another object of the present invention is to provide a diode-pumped microlaser that can be operated over a wide temperature range without requiring temperature control components. Another object of the present invention is to provide a diode-pumped laser transmitter that generates a pulsed laser beam with a high pulse repetition rate for rangefinding at extended ranges. Another object of the present invention is to provide a diode-pumped microlaser, which is lightweight and battery-operated. Yet another object of the present invention is to design a microlaser which is easy to use and is comparatively cost-effective to manufacture.